Microalgal-based urea wastewater treatment with p-Hydroxybenzoic acid enhances resource recovery and mitigates biological risks from Bisphenol A

Efficient nutrient recovery from source-separated urine is vital for wastewater treatment, with microalgae as a promising solution. However, bisphenol A (BPA) in urine can hinder microalgal resource recovery and pose water quality risks. The role of plant hormones in enhancing microalgal growth and pollutant removal is known, but their impact on BPA-laden urine treatment is not well-studied. Here, we explored para-hydroxybenzoic acid (p-HBA) in Chlorella for treating diluted urine with BPA. p-HBA boosted photosynthesis and glycolysis, increasing pyruvate and ATP production and enhancing microalgal growth by 45.7 %. It also optimized nitrogen metabolism, raising urea and nitrogen consumption by 35 % and 65 %, respectively, and protein content by 23.1 %. Enhanced oxidase and transferase expression improves BPA degradation by 40 %. Additionally, ARGs and plasmid abundance decreased by 24.3 % and 37.5 %, respectively, reducing the risk of ARG dissemination. This study shows that p-HBA significantly improves the efficiency and safety of urine resource recovery, offering a promising strategy for sustainable wastewater treatment.